TWI770161B - Optical measurement apparatus - Google Patents

Abstract

[Problem] The range of luminance that can be measured by the optical measuring device is increased without complicating the optical measuring device. [Solution] In the optical measuring device, the optical sensor receives the light from the display, and outputs the photocurrent corresponding to the light. The integrator continuously integrates the photocurrent in time and outputs the integrated signal. The required accuracy for the measurement value, the approximate brightness of the light, and the period of time change of the brightness and chromaticity of the light are acquired. The exposure time is determined according to the required accuracy and estimated brightness. The integration time is determined so that the integrator does not saturate and the exposure time becomes a common multiple of the period and the integration time. The integrator is controlled such that the exposure period is formed by at least one integration period, the length of the exposure period becomes the determined exposure time, the individual lengths of the at least one integration period become the determined integration time, and the integrator integrates during the at least one integration period. The photocurrent is integrated, and at least one integrated signal is respectively output. The calculated value is calculated based on at least one integrated signal.

Description

Optical measuring device

The present invention relates to an optical measuring device.

In an optical measuring device that measures the brightness and chromaticity of a display, the light sensor receives the light from the display, outputs a photocurrent corresponding to the received light, and the integrator integrates the output photocurrent to output an integrated signal , and the calculation unit measures the measured value based on the output integral signal. However, there is a restriction on the integration time indicating the length of the integration period during which the integrator integrates the optical signal.

The luminance and chromaticity of a display contain transient responses that vary periodically over time. Therefore, the measurement of the luminance and chromaticity of the display has to be performed in synchronization with the periodic time changes of the luminance and chromaticity of the display. Therefore, the integration time is limited to an integer multiple of the period of the temporal variation of the luminance and chromaticity of the display.

The period of the time variation of the luminance and chrominance of the display corresponds to the inverse of the frame rate or the length of the vertical synchronization (Vsync) period. For this reason, the integration time is limited to the inverse of the frame rate or an integer multiple of the length of the Vsync period. Among them, flickering occurs in principle in a liquid crystal display (LCD) that is inversion driven for burn prevention. For this reason, when an optical measuring device measures the brightness and chromaticity of an LCD, in order to measure the brightness and chromaticity accurately without being affected by flicker, the period of time change of the brightness and chromaticity is regarded as a frame 2 times the inverse of the rate or 2 times the length of the Vsync period, the integration time is limited to an integer multiple of that period.

In an optical measuring device, in order to increase the range of measurable luminance, a plurality of gains can be selected by the integrator, and the selected gain can be changed when the exposure is not appropriate. For example, gain down or gain up is performed when the exposure exceeds or falls short of an appropriate exposure, respectively. The technique described in Patent Document 1 is one example, and can measure a wide luminance range from low luminance to high luminance while realizing a high S/N ratio.

In addition, in order to increase the range of measurable luminance in other optical measuring devices, a neutral gradation filter (ND filter) can be inserted into the optical path of the light incident on the optical sensor, and when the exposure exceeds an appropriate In the case of exposure, a neutral gradation filter is inserted into the light path to reduce the amount of light incident on the photosensor. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2005-321313

[Problems to be Solved by Invention]

Among them, in order to increase the range of measurable luminance, the conventional optical measurement device has the following problems: it is necessary to make a large number of gains selectable in the integrating circuit, and it is necessary to provide a dimming mechanism for inserting an ND filter ( ND agency). Therefore, in order to perform correction for fluctuations in the measurement environment, individual variability of the measurement object, and the like, a large number of correction values and calculations are required, and a memory capacity for this is required. For example, a large number of offsets, gain corrections, environmental correction values, etc. corresponding to a large number of gains, respectively, are required.

In particular, when an optical measuring device measures the luminance and chromaticity of a display, since the integration time is limited as described above, the appropriate exposure changes with the length of the Vsync period, and the saturation value with respect to the luminance changes. For this reason, the number of necessary gains increases, and the load applied to the optical measuring device increases.

It is also possible to increase the range of luminance that can be measured through a small number of gains by increasing the gain spacing in the selectable small number of gains, the gain spacing indicating the difference between two adjacent gains. Among them, when the gain pitch is increased, the selected gain has a problem of underexposure measurement conditions of appropriate exposure.

The invention described below aims to solve this problem. The problem to be solved by the invention described below is to increase the range of luminance that can be measured by the optical measurement device without complicating the optical measurement device. [Technical means to solve problems]

In the light measuring device, the light sensor receives the light from the display, and outputs the photocurrent corresponding to the light, and the integrator continuously integrates the photocurrent in time to output the integrated signal.

The required accuracy for the measurement value, the approximate brightness of the light, and the period of time change of the brightness and chromaticity of the light are acquired.

The exposure time is determined according to the required accuracy and estimated brightness. The integration time is determined so that the integrator does not saturate and the exposure time becomes a common multiple of the period and the integration time.

The integrator is controlled such that the exposure period is formed by at least one integration period, the length of the exposure period becomes the determined exposure time, the individual lengths of the at least one integration period become the determined integration time, and the integrator integrates during the at least one integration period. The photocurrent is integrated, and at least one integrated signal is respectively output.

The calculated value is calculated based on at least one integrated signal. [Compared to the efficacy of the prior art]

According to the invention described below, the range of luminance that can be measured by the optical measuring device can be increased without complicating the optical measuring device.

The objects, features, aspects, and advantages of this invention will become clearer from the following detailed description and accompanying drawings.

1 Optical Measuring Device Fig. 1 is a block diagram showing the optical measuring device according to the first embodiment. FIG. 2 is a flowchart showing the flow of measurement performed by the optical measurement device according to the first embodiment.

The optical measurement device 1000 shown in FIG. 1 measures the luminance and chromaticity of the display, and includes a photo sensor 1020 , an integrator 1021 , a control unit 1022 , and a peripheral unit 1023 . The optical measurement device 1000 may include components other than these components.

In the light measuring device 1000, the light sensor 1020 receives light from the display, and outputs a photocurrent corresponding to the received light. In addition, the integrator 1021 integrates the output photocurrent, and outputs an integration signal corresponding to the amount of electric charge accumulated through the integration. Furthermore, the control unit 1022 calculates the measured value based on the output integral signal.

The integrator 1021 includes an integrating circuit 1040 , an integrating circuit 1041 , a switch 1042 , and a switch 1043 .

The integrating circuits 1040 and 1041 integrate the photocurrent. The switches 1042 and 1043 switch the integrating circuit for integrating the photocurrent between the integrating circuit 1040 and the integrating circuit 1041 under the control of the control unit 1022 . To this end, the integrator 1021 can integrate the photocurrent continuously in time without interruption.

It is also possible for the integrator 1021 to have a plurality of selectable gains. Thereby, the range of measurable luminance can be further increased.

The control unit 1022 is a computer that operates according to the installed program, and includes a required accuracy acquisition unit 1060 , an estimated luminance acquisition unit 1061 , a period acquisition unit 1062 , an exposure time determination unit 1063 , an integration time determination unit 1064 , and an integrator control unit 1065 and the calculation unit 1066. The hardware that executes the program may also not be responsible for all or part of the processing that the computer is responsible for.

The peripheral portion 1023 includes a display portion 1080 and an operation portion 1081 .

The measurement system executes steps S101 to S105 shown in FIG. 2 in response to the reception of the measurement command from the operator.

In step S101, measurement conditions are acquired. The measurement conditions can be acquired from an operation on a hardware switch included in the operation unit 1081 , or from an operation performed on the operation unit 1081 with respect to a graphical user interface (GUI) displayed on the display unit 1080 .

For the acquisition of the measurement conditions, the required accuracy acquisition unit 1060 acquires the required S/N ratio for the measured value. The required accuracy acquisition unit 1060 accepts the specification of one mode included in the three modes, namely the high-precision mode, the standard mode, and the high-speed mode, which correspond to the three required S/N ratios, respectively, and acquires the mode corresponding to the specified mode. The required S/N ratio. The method of obtaining the required S/N ratio can also be changed. For example, the required accuracy acquiring unit 1060 may receive the specification of one accuracy range included in the plurality of accuracy ranges corresponding to the plurality of required S/N ratios, and acquire the required S/N corresponding to the specified accuracy range. N ratio. The accuracy range is expressed by, for example, "...% or less", "...% to...%", or the like. The required accuracy other than the required S/N ratio can also be obtained.

In addition, in obtaining the measurement conditions, the period obtaining unit 1062 obtains the Vsync time, which is the length of the vertical synchronization (Vsync) period that corresponds to the period of time changes in luminance and chromaticity of the display. The Vsync time is acquired from an operation performed on the GUI displayed on the display unit 1080 by the operation unit 1081 . The Vsync frequency can also be obtained, and the Vsync time can be obtained from the obtained Vsync frequency. The acquisition method of the Vsync time can also be changed. For example, the Vsync signal may be input to the period obtaining unit 1062, and the period obtaining unit 1062 may obtain the Vsync time according to the input Vsync signal. When the luminance and chromaticity of the liquid crystal display subjected to inversion driving are measured, instead of the Vsync time, a time twice as long as the Vsync time, which corresponds to the period of the temporal changes in the luminance and chromaticity of the liquid crystal display, is obtained.

Next, in step S102, the approximate brightness of the light from the display is obtained. Step S102 and step S101 may also be performed simultaneously.

The integrator control unit 1065 controls the integrator 1021 to obtain the estimated luminance. The control is performed in such a manner that the integrator 1021 integrates the photocurrent in an initial integration period preceding a plurality of integration periods, which will be described later, and outputs an initial integration signal. In addition, the estimated luminance obtaining unit 1061 obtains the estimated luminance of the light from the display from the initial integration signal. It doesn't matter if the initial credit period is short. The method of obtaining the estimated brightness can also be changed. An example thereof will be described later.

Next, in step S103, measurement conditions are determined.

In determining the measurement conditions, the exposure time determination unit 1063 determines the exposure time based on the acquired required S/N ratio and estimated brightness. The exposure time can be changed according to the required S/N. The exposure time can be determined by using the required S/N ratio and the estimated brightness as a function of variables, or it can be determined by a look-up table (LUT). This function is, for example, a function represented by the formula (1). f (required S/N ratio, estimated luminance) included in the formula (1) is an integer. This LUT is used, for example, as a look-up table for determining the exposure time based on the required S/N ratio and the estimated luminance shown in FIG. 3 .

Exposure time = Vsync time × f (required S/N ratio, estimated brightness)...(1)

In addition, in the acquisition of the measurement conditions, the integration time determination unit 1064 determines the maximum non-saturated integration time based on the acquired estimated luminance. This maximum non-saturated integration time ensures an appropriate integration of the S/N ratio because the integrator 1021 is not saturated. time limit. In addition, the integration time determination unit 1064 determines the integration time and the number of repetitions so that the integration time is shorter than the determined maximum unsaturated integration time and the determined exposure time becomes a common multiple of the acquired Vsync time and the integration time. Thereby, the integration time in which the integrator 1021 is not saturated and the exposure time becomes a common multiple of the Vsync time and the integration time is determined.

The integration time is preferably the longest one that satisfies the aforementioned conditions of equations (2) and (3). In addition, the common multiple is preferably the least common multiple. Thereby, the electric charge accumulated in the integrator 1021 is increased within the range where the integrator 1021 is not saturated, and the S/N ratio is improved.

Number of repetitions = Int (exposure time/maximum non-saturated integration time) + 1...(2) Integration time = exposure time/number of repetitions...(3)

Although the determination of the exposure time, the determination of the maximum non-saturated integration time and the determination of the integration time are performed in different procedures, they can also be performed in the same procedure. For example, the integration time can also be directly determined by the LUT shown in FIG. 4 that determines the integration time according to the required S/N ratio, the Vsync frequency, and the estimated brightness in a manner that meets the aforementioned conditions.

Next, in step S104, measurement is performed.

In the measurement, the integrator control unit 1065 controls the integrator 1021 . The control system is performed in such a manner that the exposure period is formed by a plurality of integration periods, the number of the plurality of integration periods is the determined number of repetitions, the length of the exposure period is the determined exposure time, and the individual lengths of the plurality of integration periods are When the integration time is determined, the integrator 1021 integrates the photocurrent in a plurality of integration periods, and outputs a plurality of integration signals, respectively. Thereby, the measurement under the determined measurement conditions is performed.

Next, in step S105, calculation and output of the measured value are performed.

In the calculation and output of the measured value, the calculation unit 1066 obtains a plurality of integral signal values respectively representing the magnitudes of the outputted plurality of integral signals, and converts the average value of the obtained plurality of integral signal values into a value per unit time, The value obtained by conversion is subjected to necessary calculation processing to calculate the measured values of luminance and chromaticity. Thereby, the measured values of luminance and chromaticity are calculated from a plurality of integrated signals. It is also possible to change the calculation method of the measured values of luminance and chromaticity. In addition, the calculation unit 1066 outputs the calculated values of luminance and chromaticity.

According to the optical measuring device of the first embodiment, the number of selectable gains can be reduced, the load applied to the optical measuring device can be reduced, and the optical measuring device can be simplified. For this reason, the range of luminance that can be measured by the optical measuring device can be increased without complicating the optical measuring device.

2. Relationship between exposure time, integration time, and Vsync time in measurement conditions. Each of FIGS. 5 and 6 is a display that is the object of measurement using the optical measurement device of the first embodiment and the optical measurement device. An example of the time change of the state of the integrator is shown in the timing diagram.

FIG. 5 shows an example when the Vsync frequency of the display is high. FIG. 6 shows an example when the Vsync frequency of the display is low.

In the example shown in FIG. 5 , the exposure period 1100 having the exposure time required to secure the required S/N ratio is equally divided into eight Vsync periods 1120 . The Vsync time is, for example, about 1 millisecond to 2 seconds. In addition, the exposure period 1100 is equally divided into five integration periods 1140 . For this reason, the exposure time becomes a common multiple of the integration time and the Vsync time. The integration time is shorter than the maximum non-saturating integration time.

In the example shown in FIG. 6 , the exposure period 1160 having the exposure time required to secure the required S/N ratio is equally divided into four Vsync periods 1180 . The Vsync time is, for example, about 1 millisecond to 2 seconds. In addition, the exposure period 1160 is equally divided into five integration periods 1200 . For this reason, the exposure time becomes a common multiple of the integration time and the Vsync time. The integration time is shorter than the maximum non-saturating integration time.

3. Another example of the method of obtaining the estimated brightness FIG. 7 is a timing chart showing an example of the temporal change of the state of the optical measuring device and the integrator included in the optical measuring device according to the first embodiment.

As shown in FIG. 7( a ), the state of the optical measurement device 1000 changes from the standby state 1220 to the measurement state 1240 at the time point T1 when the measurement command is received from the operator, and changes from the measurement state 1240 at the time point T2 when the exposure time elapses from the time point T1 Change to standby state 1260 .

In addition, as shown in FIG. 7( b ), the state of the integrator 1021 changes from the state 1280 performing the integrating circuit reset operation to the state 1300 performing the integrating operation at the time point T1, and changes from the state 1300 performing the integrating operation at the time point T2 State 1320 for the reset action of the integrating circuit. Therefore, when the integrator 1021 is in the standby states 1220 and 1260, the integrator 1021 is in the states 1280 and 1320 in which the integrating circuit reset operation is performed, respectively, and in the case where the optical measurement device 1000 is in the measurement state 1240, the integrator operation is performed. Status 1300.

The integrator 1021 is in the states 1280 and 1320 in which the resetting operation of the integrating circuit is performed, and can also integrate the optical signal at all times, and can output the integrated signal. For this reason, the integrator control unit 1065 may control the integrator 1021 to integrate the photocurrent during the repeatedly coming standby integration period 1340 and output the standby integration signal, and the estimated luminance acquisition unit 1061 may control the integrator 1021 immediately before the exposure period. The coming integration period during standby is regarded as the initial integration period, and the estimated brightness is obtained. As a result, the estimated luminance is obtained before the time point T1 when the measurement is started, so that the time required for the measurement is shortened. The length of the integration period 1340 during the standby time that comes repeatedly may be the shortest time that can be set.

Although the present invention has been described in detail, the above-mentioned description is illustrative in all respects, and the present invention is not limited thereto. Innumerable modifications not illustrated should be conceivable without departing from the scope of the present invention.

1000‧‧‧Light Measuring Device 1020‧‧‧Photo Sensor 1021‧‧‧Integrator 1022‧‧‧Control Unit 1060‧‧‧Required Accuracy Acquiring Unit 1061‧‧‧Approximate Brightness Obtaining Unit 1062‧‧‧Period Acquiring Unit 1063‧‧‧Exposure time determination part 1064‧‧‧Integration time determination part 1065‧‧‧Integrator control part 1066‧‧‧Calculation part

FIG. 1 is a block diagram illustrating the optical measuring device according to the first embodiment. [ Fig. 2 ] A flowchart showing the flow of measurement performed by the optical measurement device according to the first embodiment. [ Fig. 3] Fig. 3 is a diagram illustrating a look-up table (LUT) for determining the exposure time based on the required S/N ratio and the estimated brightness in the optical measuring device of the first embodiment. 4 is a diagram illustrating a look-up table (LUT) for determining the integration time based on the required S/N ratio, the vertical synchronization (Vsync) frequency, and the estimated luminance in the optical measuring device of the first embodiment . [ Fig. 5] Fig. 5 is a timing chart showing an example of temporal changes in the state of the display which is the object of measurement using the optical measuring device according to the first embodiment and the state of the integrator included in the optical measuring device. [ Fig. 6] Fig. 6 is a timing chart showing an example of temporal changes in the state of the display which is the object of measurement using the optical measuring device according to the first embodiment and the state of the integrator included in the optical measuring device. [ Fig. 7] Fig. 7 is a timing chart showing an example of temporal changes in the state of the optical measurement device and the integrator included in the optical measurement device according to the first embodiment.

1000‧‧‧Optical measuring device

1020‧‧‧Light Sensor

1021‧‧‧Integrator

1022‧‧‧Control Department

1023‧‧‧Peripheral Department

1040‧‧‧Integrator circuit

1041‧‧‧Integrator circuit

1042‧‧‧Switch

1043‧‧‧Switch

1060‧‧‧Required Accuracy Acquiring Department

1061‧‧‧Approximate brightness acquisition department

1062‧‧‧Cycle Acquisition Department

1063‧‧‧Exposure Time Determination Department

1064‧‧‧Integration Time Determination Department

1065‧‧‧Integrator Control Section

1066‧‧‧Calculation Department

1080‧‧‧Display

1081‧‧‧Operation Department

Claims (7)

An optical measuring device for measuring the brightness and chromaticity of a display, the optical measuring device comprising: a light sensor for receiving light from the display and outputting a photocurrent corresponding to the light; an integrator for temporally continuous The photocurrent is integrated and an integrated signal is output; a required accuracy acquisition unit acquires the required accuracy of the measured values of the luminance and chromaticity before measurement; an approximate luminance acquisition unit acquires the approximate luminance of the light before measurement; period an acquisition unit that acquires a period of time change of the luminance and chromaticity of the light before measurement, and an exposure time determination unit that acquires the required accuracy and the approximate brightness acquired by the required accuracy acquisition unit before measurement The brightness is estimated to determine the exposure time of the light sensor; the integration time determination unit is used to determine the integration time of the integrator before the measurement in such a way that the integrator is not saturated and the exposure time becomes a common multiple of the period and the integration time determine; an integrator control unit that controls the integrator so that the exposure period of the photosensor is formed by at least one integration period, the length of the exposure period becomes the exposure time, and the individual of the at least one integration period The length of is the integration time, and in the measurement, the integrator is in the The photocurrent is integrated in at least one integration period, and at least one integrated signal is respectively output; and a calculation unit calculates the measured value according to the at least one integrated signal. The optical measuring device according to claim 1, wherein the integrator control unit controls the integrator so that the integrator integrates the photocurrent in an initial integration period preceding the at least one integration period, and outputs an initial integration signal, and the integrator outputs the initial integration signal. The estimated brightness obtaining unit obtains the aforementioned estimated brightness from the aforementioned initial integration signal. The optical measuring device according to item 2, wherein the integrator control unit controls the integrator to integrate the photocurrent during a repeatedly coming standby integration period, and outputs a standby integration signal, and the initial integration period is set at The integration period on standby comes immediately before the aforementioned exposure period. The optical measuring device according to any one of Items 1 to 3, wherein the common multiple is a least common multiple. The optical measuring device according to any one of Items 1 to 3, wherein the exposure time can be changed according to the required accuracy. The optical measurement device according to any one of items 1 to 3, wherein the integrator has a plurality of selectable gains. The optical measuring device according to claim 1, wherein the exposure time determination unit determines the exposure time by multiplying the length of the cycle by an integer determined according to a predetermined relationship between the required accuracy and the estimated brightness, and the integration time determines The part determines the maximum non-saturating integration time as the upper limit of the reasonable integration time that the integrator does not saturate and can ensure the required accuracy according to the above-mentioned estimated brightness, and divides the above-mentioned exposure time by the above-mentioned maximum non-saturating integration time. The value obtained by adding 1 to the integer below the decimal point of the value is determined as the integration time by dividing the value obtained by the exposure time, and the optical measuring device of item 1 is requested.

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